How to calculate the number of LEDs for the power supply and vice versa?

Question

Batteries

It is necessary to illuminate small figurines either from batteries or from 5V 1A power supplies, now I have a ready-made solution in the form of a backlight of 5 diodes connected to an arduino. I would like to transfer them to the power supply, how can I calculate which resistors to put, if I know that there are 5 LEDs, specifications 3V, 20mA - and they need to be connected to a 5V 1A power supply.

Answer 1

There are special calculators for calculating LEDs.
Here is your case.

Answer 2

the voltage is 5 V, the excess is dissipated by a ballast resistor so that (1-0.045) * 0.9 / 0.02 = 43 LEDs , of
course, if we consider that they will all burn at the same time, otherwise more is possible. It is also unnecessary to forget that the maximum output load current is 40mA, but it costs more than 25mA. Those. if you turn on several LEDs in parallel, you need a transistor

Answer 3

As already mentioned above, there are special calculators. In theory, you can read what-how to calculate here: ledjournal.info/spravochnik/raschet-resistora-dlya...

Answer 4

Voltage at which the LED will light × number of LEDs = Voltage at which all will light,
Battery output current - result
Example:
LED on: 0.5 v
Qty: 10 pcs.
Battery on: 10 v
0.5 × 10 = 5 (if I'm not mistaken)
10 - 5 = 5
The result of the battery is enough